Plasticization of polymerized styrene



Patented Jan. all, E7

PLASTICIZATIDN @F 3 2,4 4,491 orrica POLYMERIZED Amni- James Warner and Archibald Alan N w. London W. C. 2, England, assi'gnors to International Standard Electric Corporation, New

York, N. Y.

No Drawing. Original application February 11,

1938, Serial No. 190,032. Divided and this application July 26, 1941, Serial No. 404,108. In

Great Britain February 19, 1937 4 Claims. (oi. 260-86) 1 erties; particularly as regards iusi'bility and fiexibility which vary throughout a wide range. The polymers formed at high temperatures are readily fusible, but are very brittle when cold, whereas polymers formed at room temperature are in- !uzible and relatively tough. All types of polymers oi styrene have excellent insulating proper-' ties, particularly at very high frequencies of the order of cycles andhigher. It is, however, necessary for many electrical purposes that the material be made appreciably more flexible and less brittle, e. g., in the production of threads and strands for insulating purposes in coaxial cable and films for lapping and general insulation purposes. Y

Manyproposals have previously been made for theuse 01' many diflerent materials as plasticizers of polymerized styrene. In many cases these materials have been stated to plasticize any of a wide range of plastics such as cellulose esters and ethers, .and polymerized vinyl resins generally. Due to the varied chemical composition of the plastics and plasticizers, it has been found-that in many cases no plasticizing eflect takes place, e. g., a plasticizer for one compound is not necessarily a plasticizer ior another. Y It has alsobeen found that in some cases there isran appreciable loss of these plasticizers in a comparatively short time with a corresponding falling of! in the plasticizing eflect. The boiling \point of a compound may be taken as giving for practical purposes a, rough criterion as to the vapour pressure.

According to the present invention a method of plasticizing polymerized styrene consists in adding :thereto a. chemically stable homocyclic carbon compound having two or three fused rings that has a boiling point higher than 240 C. that possessesa low electric moment; and is capable of swelling polystyrene. By a stable compound is meant a compound that does not readily alter its chemical composition on exposure to air. I By a ruins containing 29a of phenanthrene show the addition of sufiicient of the compound to:

polystyrene to increase its plasticity five told does not increase .the poweri'actor at 10 cycles a second more than five times. (The poweriactor'oi I polystyrene 0nd).

The plasticizer may be. incorporated withthe itself is 0.002 at. 10? cycles per secpolystyrene, either by adding to the monomerv 1 before polymerization, by hot rolling with the polymerized styrene, or by dissolving along with the polymerized-styrene in a mutual solvent and subsequently evaporating the solvent.

The following comparative figures of the action of various substances upon polymerized styrene have been obtained by dissolving 30 grams of the p lymerized styrene sold under the trade name of Trolitul in 100 cc. of benzene, shaking 01724 hours and filtering. Such a solution has a viscosty of 330 centistokes at 20C. To grams I of the filtrate there was added 'sumc'ient of. the substance to be tested to give the desired per-' centage, 50. cc. of benzene was added and the whole mixture shaken to eflect solution. "3 ec.ioi.

this solution was run over the surface of clear mercury in a crystallizing dish, the resulting, film allowed to remain on the mercury for 48 hours and then removed and stored for a further 5 days before testing in' order to ensure that the last traces of solvent had been removed. The films tained under a tension or 200 grams. The jaws were then moved to and fro through an angle oi 280 so as to bend the strip round the brass rods at each reciprocation. The number or bends before the strip breaks is a measure oi the pies-'- ticity of the material oi!- the strip. The number oi bends for polystyrene itself without the addition of other substances was 8.

As a guide to the percentages given:

Example I Phenanthrene added in-diilerent percentages to polystyrene gave the number oi bends shown below:

Percent phe'nanthrene No.0! bends 0.. .Q a I of plasticizer that may be-used, the following examples are signs of crystals indicating that the bility had been reached.

- Example If Example III a-n-Propylnaphthalene increases the plasticity of polystyrene in percentages up to 15% but higher percentages do not cause any further increase in plasticity. The power factor of the mixture containing 15% is 0.0006.

Example IV I s Methylnaphthalene increases the plasticity limit of coinwhen added in amounts at least up to 25%. l biamounts greater than however, the power factor exceeds 0.001.

The plasticiers according to the invention may be usefully contrasted with certain substances excluded from the invention.

Polychlorinated diphenyls sold under the trade names Aroclor" and Permitol have been used as plasticizers, but they are unsymmetrical compounds and increase the power factor of polystyrene unduly. Thus 6% of these substances gave a test result of 40 bends but the power factor is raised to 0.0015 at 10' cycles per second.

Dibutyl phthalatel has frequently been suggested as a plasticizer, but it n a high electric moment. 2.7% is suiilcient to give a test result of 40 bends but the power factor is 0.0015 at 10 cycles per second 10% of 9-bromophenanthrene sult of 33 bends only and the power factor is raised to 0.0033 at 10 cycles per second.

10% of methyl-p-naphthyl ketone gave a test result of 63 bends but raised the power factor to 0.0126 at 10 cycles per second.

' Bezene, toluene, and" xylene have been suggested for use as plasticizers, but owing to their low boiling point, the plasticity is rapidly lost with time. The same thing is true of di-phenyl and naphthalene (which are also excellent plasticizers) as shown by the following results:

:Yllfethyl abietate has also been claimed and while it is useful for temporary purposes it is not of permanent value due to its-oxidizing to a brittle resin by taking up atmospheric oxygen and thus losing its plasticizing power.

certain plasticizers according to the invention is I shown in the following:

N6. of bonds Plnsticiter Quantity Age of him bang e frac- I! Per cent Week:

Phenanthrene I l. 42 4 '41 l6 1 89 4 as a .80 i2 88 Isoamyinaphthalene.... 5 g l5 l 132 gives a test re- ,4 On the other hand the effect of time with The following table shows the properties of certain substances that may be used in' accordance with the invention as plasticizers:

Polymerized styrene plasticized by the addi- I tion of any of the compounds according to the invention is particularly well adapted for the con-= struction of dielectric wave guides, for use as insulation in coaxial cables, and for use as a dielectric of condensers particularly those intended for circuits in which very high frequency cur-' rents flow.

What is claimed is:

1. An improved electrical high frequency insulation of plasticized polymerized styrene admixed with a hydrocarbon substitution compound of I naphthalene having not-more than 5 carbon atoms in the chain, and characterized by a power factor of lessthan .001 'at 10 cycles.

2. An improved electrical high frequency insulation of plasticized polymerized styrene admixed with an amyl naphthalene, and characterized by apower factor of less than .001 at 10 cycles.

0. An improved electrical high frequencyinsulation of plasticized polymerized styrene admixed with between 1% and 20% of an amyl naphthalene, and characterized by a power factor of tiialene, and characterized by a power factor of less than .001 at 10 cycles.

ARTHUR 5S WARNER. ALAN NEW. A 

